1. Field of the Invention
The present invention relates to a reception synchronization control device and a reception synchronization control method for controlling reception synchronization of demodulated signals (for example, analog modulated signals of at least two channels) to be established when a radio communication apparatus such as a cellular phone receives and demodulates a phase-modulated signal transmitted by a phase modulation, and relates to a program for making a computer execute this reception synchronization control method.
At the time of receiving a phase-modulated signal transmitted by using a QPSK (quadrature phase-shift keying) modulation, as one kind of a phase modulation of digital data, and demodulating the phase-modulated signal into analog demodulated signals of two channels in a mutually orthogonal relationship, it is necessary to extract the original four-value digital data from two-channel analog demodulated signals without an error. It is also necessary to confirm whether or not the reception of the analog demodulated signal is synchronized in all frequencies used by carrying out an adjustment test of a reception card on which a demodulator of a cellular phone and the like is mounted. The present invention describes a method of establishing a state of reception synchronization, by confirming by a simple method whether or not a reception of the analog demodulated signal is synchronized.
2. Description of the Related Art
In general, in the manufacture of a radio communication apparatus such as a cellular phone, a reception card on which a demodulator of the apparatus is mounted is manufactured separately from another card within the radio communication apparatus. Therefore, at the stage of carrying out the adjustment test of the reception card, the reception card within the radio communication apparatus is separated from the other card. Accordingly, a state of reception synchronization needs to be established by confirming whether or not the reception of the reception card is synchronized, for each card.
In order to facilitate the understanding of a problem in confirming whether or not reception is synchronized by carrying out an adjustment test of reception synchronization of the reception card within the radio communication apparatus according to a conventional system, a process in which a reception card testing device according to the conventional system is used to carry out the adjustment test of reception synchronization of the reception card will be explained with reference to FIG. 1 that will be described later in the “BRIEF DESCRIPTION OF THE DRAWINGS”.
A block diagram of a configuration of a reception card testing device according to a conventional reception synchronization establishing method is illustrated in FIG. 1. More specifically, FIG. 1 shows a schematic configuration of the reception card testing device that carries out an adjustment test of each reception card as a single unit within a radio communication apparatus such as a cellular phone used in a W-CDMA (Wideband Code Division Multiple Access) format.
As shown in FIG. 1, the radio communication apparatus, such as a cellular phone, usually includes a demodulator (that is, a demodulating unit) 1 that receives a phase-modulated signal S-QPSK transmitted by a phase modulation of digital data such as a QPSK modulation system, and demodulates this phase-modulated signal into two-channel analog demodulated signals SA-I and SA-Q; and an analog/digital converter (an A/D converter) 2 that converts the analog demodulated signals SA-I and SA-Q output from the demodulator 1 into digital demodulated signals SD-I and SD-Q. The analog demodulated signals SA-I and SA-Q are substantially cyclical two-channel signals mutually in an orthogonal phase relationship, and are expressed by a change of output voltage V relative to time (r).
Further, an output signal processor 9 is provided at the output side of the analog/digital processor 2. This output signal processor 9 reproduces digital data of a satisfactory signal-to-noise ratio (S/N ratio), by carrying out various kinds of signal processes such as a calculation of bit error rate and a bit error correction to the digital demodulated signals SD-I and SD-Q output from the analog/digital converter (A/D converter) 2.
For the radio communication apparatus, such as a cellular phone, a reception card mounted with the demodulator 1 and the analog/digital converter 2 is manufactured separately from another card mounted with the signal processor 9. Confirmation of whether or not reception of a reception card is synchronized and adjustment of reception synchronization are carried out before the product is shipped. At the stage of carrying out the adjustment test of reception synchronization of a reception card, the adjustment test of the reception card is carried out as a single unit in a state that the reception card is separated from another card. It should be noted that the reception card itself does not have a function of carrying out an adjustment test of reception synchronization. Therefore, in carrying out the adjustment test of reception synchronization of a reception card, the reception card needs to be able to artificially carry out the adjustment test of reception synchronization in some way.
Therefore, in the reception card testing device according to the conventional reception synchronization establishing method, an oscilloscope or the like to monitor reception synchronization of the reception card is connected to the output of the analog/digital converter 2 within the reception card, as shown in FIG. 1. This oscilloscope usually includes a signal display controller 3 and a polar coordinates display 4, and is able to display polar coordinates of digital demodulated signals SD-I and SD-Q output from the analog/digital converter 2. The signal display controller 3 processes the digital demodulated signals SD-I and SD-Q output from the analog/digital converter 2, and generates signal data SP-I and SP-Q to display the polar coordinates. The polar coordinates display 4 displays the signal data SP-I and SP-Q output from the signal display controller 3 onto the display surface (i.e., display screen) of the polar coordinates. Accordingly, the reception card is able to confirm a reception synchronization state.
On the display screen of the polar coordinates display 4 shown in FIG. 1, digital data C (0, 0), C (0, 1), C (1, 0), and C (1, 1) at four points (shown by black circles), each of which has a phase difference of 90 degrees from the phase of the adjacent point, are displayed in a first quadrant to a fourth quadrant, respectively of I-Q coordinate space, including an I axis and Q axis. The digital data at the four points on the display screen change with time due to noise, etc. Therefore, the digital data are displayed in a form in which each of the four points has a certain two-dimensional broadening from an ideal point on the display screen.
In carrying out the adjustment test of reception synchronization of a reception card using the reception card testing device shown in FIG. 1, conventionally, a constellation position of digital data appearing most densely on the display screen is visually estimated, while visually monitoring digital data displayed with a certain spread in the I-Q coordinate space on the display screen of the oscilloscope. Next, parameters such as voltage value and potential on the display screen of digital data are changed based on the estimated constellation position, thereby adjusting the state of reception synchronization of the reception card, and confirming whether or not the reception of the analog demodulated signals of two channels is synchronized. Finally, when it is confirmed that the reception of the analog demodulated signal is synchronized, the phases of the digital data are locked, thereby establishing a state of reception synchronization. In this case, in order to guarantee performance of the radio communication apparatus as a product, the state of reception synchronization needs to be established by confirming whether or not the reception of the analog demodulated signal is synchronized in all frequencies used.
The “constellation” refers to a portion formed by the four points most densely displayed on the display screen of the oscilloscope in the form of an asterism or constellation, when plural signal data are displayed in the polar coordinates.
In carrying out the adjustment test of reception synchronization of the reception card using the conventional method, an operator must adjust the state of reception synchronization of the reception card while continue to monitor the digital data at four points displayed on the display screen of the oscilloscope. Further, in order to guarantee the performance of the product, the operator must confirm whether or not the reception of the analog demodulated signal is synchronized in all frequencies used. Therefore, the operator is required to spend time adjusting the state of the reception synchronization of the reception card. Consequently, the adjustment work of the state of the reception synchronization becomes troublesome.
When plural operators carry out an adjustment test of the reception synchronization, variations in the adjustment may occur depending on the sense of individual operators. Therefore, it is difficult to guarantee the quality of the state of reception synchronization established by the adjustment test.
On the other hand, in order to establish a state of reception synchronization of an analog demodulated signal by automatically carrying out the test, dedicated hardware is necessary to adjust the state of reception synchronization by automatically changing parameters of voltage values and phases of digital data displayed on the display screen of the oscilloscope. However, in this case, additional cost is necessary to prepare dedicated hardware.
For reference, the following Patent Document No. 1 and Patent Document No. 2 relevant to the above conventional reception synchronization establishing method are shown as prior-art documents.
(i) Patent Document No. 1: Japanese Unexamined Patent Publication (Kokai) No. 11-331299
(ii) Patent Document No. 2: Japanese Unexamined Patent Publication (Kokai) No. 2001-24603
Patent Document No. 1 discloses a 64-QAM modulation and 256-QAM modulation analysis method, including detecting a maximum value and a minimum value of amplitudes at symbol points of an input signal; determining a gain from the detected minimum value (or the maximum value) and a prescribed value; multiplying this gain to an amplitude of the symbol points of the input signal; rotating the phase of the row of the symbol points of the input signal multiplied by the gain, by a predetermined amount; obtaining an ideal symbol point row by demodulating the symbol point row of the input signal of which phase is rotated; obtaining a correlation between this ideal symbol point row and the symbol point row of the input signal of which phase is rotated; and obtaining a positional rotation of the symbol points, a generation of an ideal symbol point row, and the above correlation, until a predetermined amount of phase rotation becomes π/4 radian (45 degrees). However, Patent Document 1 does not describe a method of establishing a state of reception synchronization by confirming whether the reception of the analog demodulated signal is synchronized at the time of receiving a phase-modulated signal transmitted by the phase modulation of digital data, such as QPSK modulation and demodulating the phase-modulated signal into analog demodulated signals of plural channels.
Patent Document No. 2 describes a method of transmitting a radio signal, by obtaining an identification number and signal quality of a radio broadcast program from a radio signal and using a propagation wave signal obtained from the best signal quality to receive a selected radio broadcast signal, in transmitting the radio signal by an orthogonal frequency division multiplexing system. However, Patent Document No. 2 does not describe a method of establishing a state of reception synchronization by confirming whether or not the reception of the analog demodulated signal is synchronized, at the time of receiving a phase-modulated signal transmitted by the phase modulation of digital data and demodulating the phase-modulated signal into analog demodulated signals of plural channels.
Therefore, none of Patent Document No. 1 and Patent Document No. 2 can solve problems generated when visually confirming whether or not reception is synchronized by carrying out the adjustment test of reception synchronization of a reception card of a radio apparatus by the conventional method.